A bit difficult to read. Perhaps where you write "effect" you mean "affect"?
Also I fail to imagine how the wings can be level in a side-slip, as you assume.
Still trying to reply: I always learned that side-slipping does increase the stall speed, however it so much increases the rate-of-descent that one still gets to the ground sooner - which is the primary goal of the manoevre (apart from the sheer excitement, of course
)